Electric motor driven liquid pump, in particular for the forced lubrication of a manual transmission for motor vehicles

ABSTRACT

An electric motor driven fluid pump for forced lubrication of a manual transmission of a motor vehicle, includes a housing having a fluid inlet and a fluid outlet, and an electronically commutated electric motor incorporated therein. The electric motor has a substantially cup-shaped magnetic rotor rotatable around a rotational axis, shaped for conveying fluid, an annular stator having a motor winding which at least partially encloses the rotor in a coaxial arrangement with respect to the rotational axis when viewed along the rotational axis, and a magnetic field sensor for detecting the position of the rotor. The housing includes a stator housing section which holds the stator, separates same from a liquid chamber in which the rotor is arranged, and extends into the rotor by a housing offset formed for receiving the magnetic field sensor.

TECHNICAL FIELD

The present invention relates to an electric motor driven liquid pump.In particular, the invention relates to a liquid pump such as used on alarge scale in modern motor vehicles for the forced lubrication ofmanual transmissions.

A manual transmission, which is arranged in the motor vehicle in a drivetrain between an internal combustion engine and vehicle wheels to bedriven, has a lubricant system for lubrication by a lubricant such astransmission oil, which lubricant system serves the purpose of fetchingthe lubricant from a lubricant sump in the transmission housing to areasto be lubricated. Included in the latter are, in particular, meshinggearwheels and bearings for rotating parts, particularly shafts andgearwheels.

In conventional lubricant systems in manual transmissions distinction isbasically made between splash lubrication, in which the gearwheels‘splash’ in the lubricant sump and during further rotation distributethe lubricant to the gearwheels and bearings, and forced lubrication byone or more pumps, which convey the lubricant from the lubricant sump byway of a duct system to the places to be lubricated. If forcedlubrication alone is provided, i.e. none of the gearwheels intentionallydips into the lubricant sump, this is termed ‘dry sump lubrication’,which by comparison with splash lubrication or combined lubrication hasthe advantage that there is no induction of air into the lubricant bythe gearwheels and thus no formation of oil foam, which can lead todisruptions in the transmission lubrication. In addition, in manualtransmissions with dry sump lubrication so-called ‘splash losses’impairing transmission efficiency are avoided.

PRIOR ART

Electric motor driven lubricant pumps are already used in the prior artfor the lubricant system of manual transmissions with dry sumplubrication (see, for example, document DE-A-10 2005 005 154).Distinction has to be made here between lubricant systems in which thelubricant is conveyed by the pump—usually a gear pump—under pressure tonozzles, by way of which the lubricant is sprayed on the places to belubricated, and lubricant systems with a pump—for example a centrifugalpump—by which the lubricant is merely conveyed to a distributor with areservoir, from where the lubricant substantially free of pressure rainsdown or drips onto mesh zones and bearing locations. The last-mentioned,low-pressure lubricant system represents the field of pump use preferredhere, in particular because it offers cost advantages by comparison withthe solution involving pressure. Thus, a filter arrangement foravoidance of nozzle blockage is redundant, susceptibility tocontamination is less overall, lower motor power can be provided for theelectric motor, etc.

Constructional details of an electric motor driven centrifugal pump forlubricant supply of a transmission are known from, for example, documentDE-A-10 2007 018 504 (FIG. 7). In this instance an electric motor and apump driven by it form a motor/pump unit, which is arranged directly inthe lubricant (‘operating medium’ in the terminology of this document)below a liquid level. The electric motor and the pump in this prior artlie in succession and the motor/pump unit is additionally surrounded bya duct system serving the purpose of conducting the intake flow alongthe surface of the electric motor, which heats up due to operation, to asuction port of the pump. Heat transfer is to be improved and thelubricant heated by thermal contact between the electric motor and thelubricant conducted therealong, so that the viscosity of the lubricantis reduced and thus also the intake resistance. As a result, theconveying rate of the pump is to be increased and thus the quantity oflubricant supplied to the lubricating points; in addition, a downwardextension of the temperature range at which the pump can still reliablyconvey lubricant is intended. A disadvantage of this prior art, however,is that the motor/pump unit together with the duct system therearounddemands a relatively large amount of space not only in radial direction,but also in axial direction. However, the available installation spaceat the bottom of the transmission housing is usually very tightlydimensioned.

In addition, an electric motor driven oil booster pump arranged withinan oil pan of an automatic transmission is known from document DE-A-102006 012 838 (FIG. 3c). In this prior art, as well, the pump and theelectric motor lie in succession, the latter being located outside theoil pan. In that case, drive of the pump takes place mechanically by wayof a shaft which passes through the wall of the oil pan and is sealedrelative to this wall. This arrangement of pump and electric motor insuccession also demands a relatively large amount of space. Moreover,use is preferably made of a brush motor, which, as such, necessarily hasto be arranged outside the oil chamber and in addition is susceptible towear.

Moreover, documents DE-A-199 34 382 and DE-A-199 56 380 disclose liquidpumps usable as cooling water pumps for the cooling circuit/heatingcircuit of a motor vehicle. These liquid pumps have an integratedelectric motor with a stator and a rotor, the stator being a claw polestator and the rotor forming an impeller of the pump. In this prior art(DE-A-199 34 382: column 3, lines 47 to 51; DE-A-199 45 380: column 4,lines 17 to 22) a magnetic field sensor (not illustrated) can beprovided, particularly for commutation of the electric motor, at alocation (not specified in more detail) where it is exposed to thevariable magnetic field of the rotating rotor.

Similarly, an electric motor driven water pump is known from DE-A-102009 049 904 (FIG. 1), in which a partition sealingly arranged between astator and a rotor unit is constructed in a simpler and more economicmanner from a corrosion-resistant material capable of being deep drawn.In that case, a substantially hollow conical retaining element isintegrally formed at a central location of the partition, which elementis provided on its side facing the rotor unit with a spherical bearingsurface for a spherical slide body for mounting the rotor unit and onits side remote from the rotor unit bounds a cavity in which atemperature and/or magnetic field sensor (not illustrated) can bereceived (see claims 9 and 10 as well as the Abstract [0027] of thedescription), so that the bearing points for the rotor unit and thesensor are necessarily arranged axially in succession with respect tothe axis of rotation of the pump.

Finally, further electric motor driven pumps which are, however, ofrelatively lengthy construction as seen along the pump rotational axisand which are used as, in particular, water pumps in heating circuitsare evident from documents DE-A-100 45 597 (FIGS. 7 and 8) and DE-A-10052 797 (FIG. 1).

What is desired is to provide particularly for forced lubrication of amanual transmission for motor vehicles, an electric motor driven liquidpump which avoids the above disadvantages and in particular has bycomparison with the outlined prior art, in a more economic design alower constructional height.

SUMMARY OF THE INVENTION

An electric motor driven liquid pump according to one embodiment of theinvention, which is usable particularly for forced lubrication of amanual transmission for motor vehicles, includes a housing, which has aliquid inlet and a liquid outlet, and an electronically commutatedelectric motor, which is received therein and which includes asubstantially cup-shaped magnetic rotor, which is rotatable about anaxis of rotation, and constructed for conveying liquid, an annularstator, which has a motor winding and which as seen along the axis ofrotation at least partly surrounds the rotor in coaxial arrangement withrespect to the axis of rotation, and a magnetic field sensor forpositional recognition of the rotor. The housing has a stator housingsection which carries the stator, separates this from a liquid chamberin which the rotor is arranged and as seen along the axis of rotationextends into the rotor by a housing offset constructed for reception ofthe magnetic field sensor.

Due to the fact that from the start the drive of the liquid pumpaccording to one embodiment of the invention is formed by anelectronically commutated electric motor as distinct from a brush motor,the susceptibility to wear and disturbance as discussed above withrespect to the prior art is absent; the liquid pump can also be freelypositioned, for example in or directly at an oil chamber of a manualtransmission.

In that regard, a particularly compact constructional form is favored atthe outset if the rotor is both a pump component (e.g. for liquidconveying) and a motor component (e.g. magnetic). Any rotatingconnection between the drive side and the pump side is thus redundant.Moreover, with respect to low constructional height of a liquid pumpaccording to the invention, the design of the stator housing section,which also separates media in the pump housing, has a special role. Onthe one hand, the stator housing section carries the annular stator insuch a way that this covers the cup-shaped rotor at least partly as seenin axial direction. On the other hand, the stator housing section hasthe housing offset which protrudes into the cup-shaped rotor and atwhich the magnetic field sensor for the electronic commutation isreceived. Through this arrangement, which can be characterized asnested, of the components relevant to drive substantially in the rotorplane with utilization as well of the rotor internal area, the liquidpump has a very flat construction. In other words, by contrast to theprior art outlined further above a pure arrangement of the individualcomponents in succession is not present, but rather an arrangementthereof of one nested in the other.

In an advantageous development of the liquid pump the housing can beflange-mounted on a liquid container by way of a flange surface externalto the pump and can have in multi-part construction, apart from thestator housing section, a pump housing section, which has the liquidinlet and liquid outlet and which together with the stator housingsection bounds the liquid chamber, and a motor housing section, whichtogether with the stator housing section bounds an electronics chamberin which at least the stator is disposed. In this embodiment the pumphousing includes in a simpler and more assembly-friendly manner, only aminimum of housing components to separate wet regions of the pump fromdry regions of the pump and to bound the latter overall relative to theliquid or environment/atmosphere, namely (a) the pump housing section asa boundary, which is permeable in defined manner by way of the liquidinlet and outlet, for the liquid, (b) the stator housing section as amedia-separating boundary between the wet liquid chamber and the dryelectronics chamber in the pump and (c) the motor housing section as aboundary relative to the rest of the environment/atmosphere.

In principle, the housing components of the liquid pump can be made froma light metal such as, for example, an aluminum alloy. However, withregard to low production costs it is preferred if the housing componentsare built as plastic material parts, which can be produced by injectiontechnology, i.e. by plastic material injection molding. A screwconnection, rivet connection or snap connection, for example, isconceivable for fastening the housing components to one another.However, for a particularly economic housing design it is preferred ifthe pump-housing and motor-housing sections produced as plastic materialparts are welded together.

Moreover, the stator housing section can have, with respect to a simpleand axially as well as radially positionally precise fastening in thehousing of the liquid pump, a stator housing flange which is clamped inplace between the pump housing section and the motor housing section andwhich additionally centers the stator housing section at the motorhousing section with respect to the axis of rotation of the rotor.

In a particularly preferred embodiment of the liquid pump a sealingelement can be provided, which—in multi-functional manner—at the sametime firstly seals relative to the liquid container at the flangesurface of the housing external to the pump (‘i.e. pump external’separation between liquid and environment/atmosphere), secondlyseparates the liquid chamber from the electronics chamber (i.e. ‘pumpinternal’ media separation) and thirdly seals the electronics chamberrelative to the environment (i.e. sealing against penetration ofmoisture or contamination of the pump).

By contrast to the current prior art, a multiplicity of seal inserts isnot required and does not have to be handled and the disadvantagesconnected therewith (e.g. assembly cost, risk of ‘migration’ ofindividual seals, etc.) are avoided without alternative measures suchas, for example, sealed welding of housing components having to beprovided at the housing. Since, in addition, the pump already carriesthe means for sealing ‘external to pump’, the assembly/flange-mountingof the pump at the liquid container is simplified. As a result, a lessexpensive pump sealing which has process security and thus alsoreliability can be achieved.

In that regard, the flange surface, which is external to the pump, ofthe housing can be provided with an encircling groove for receiving afirst sealing section of the sealing element, which protrudes by atleast one sealing lip, but preferably two sealing lips, beyond theflange surface external to the pump so as to seal relative to the liquidcontainer. A double sealing of that kind seals in a manner which isparticularly resistant to contamination and reliable. Scratches or thelike at the flange surface of the liquid container can be ‘bridgedover’; consequently, there are no special demands on cleanliness orsmoothness of the flange surface.

Moreover, the arrangement can be such that the pump housing section hasa pump housing flange at which the flange surface external to the pumpand a flange surface internal to the pump are formed at opposite sides.A flange surface internal to the pump is provided with an encirclinggroove for receiving a second sealing section of the sealing element.The second sealing section protrudes by two sealing lips beyond theflange surface internal to the pump, wherein—in a clearer and uniquefunctional assignment of the sealing lips—one sealing lip co-operateswith the stator housing section in order to separate the liquid chamberfrom the electronics chamber, while the other sealing lip co-operateswith the motor housing section in order to seal the electronics chamberrelative to the environment. In that case, the sealing lips canadvantageously compensate for different housing thicknesses—which maydiffer only due to tolerances—in the flange regions of the statorhousing section and the motor housing section.

In addition, the sealing element made from an elastomeric material, canbe attached to the pump housing section so that the sealing element is,in a more assembly-friendly manner, a captive component of the liquidpump. In principle, the sealing element can in that case be incorporatedin or plugged onto the pump housing section. However, with respect tosimple capability of production and process reliability (e.g. avoidanceof assembly errors) it is preferred if the sealing element isinjection-molded at the pump housing section to be interlocking.

For a reliable mechanically positive fixing of the sealing element tothe pump housing section there can be provided between the encirclinggroove at the flange surface external to the pump and the encirclinggroove at the flange surface internal to the pump a plurality ofopenings which are spaced apart in circumferential direction and throughwhich the elastomeric material of the sealing element isinjection-molded in order to connect the first sealing section and thesecond sealing section of the sealing element together. The sealingelement can thus advantageously be injection-molded on the pump housingsection in one working step. In the case of an overlapping or acongruent arrangement of the grooves on the two sides of the pumphousing flange the sealing arrangement is also a very compactconstruction in radial direction. Beyond that, such an arrangement, inwhich sealing with respect to two sides takes place approximately on onediameter, has the advantage that even in the case of relative ‘soft’ orflexible housing components the risk of leakages due to housingdeformation is minimized.

In an advantageous development of the liquid pump, pole sheets of thestator can be embedded in the stator housing section, which consists ofa plastics material, by plastics material injection-moldingencapsulation. As a result, an optimum heat dissipation from the motorwinding and pole sheets to the liquid chamber is made possible. At thesame time, the motor winding is electrically insulated by theinjection-molded encapsulating plastics material.

In further pursuance of one embodiment of the invention, a temperaturesensor can be integrated, preferably near the liquid outlet, in thehousing of the liquid pump, in particular received in a receiving recessin the stator housing section, as a result of which an externaltemperature sensor and the assembly cost connected therewith areeliminated in all cases. Through detection of the temperature of theconveyed liquid, a conclusion can be made about its viscosity—which inthe case of oil is important for the lubricating effect thereof—togetherwith the need for cooling and the rotational speed of the electric motorcan be suitably controlled, in which regard, for example, a tendency tohigher temperatures signals a greater need for cooling and thus arequirement for higher pump rotational speeds. Positioning of thetemperature sensor near the liquid outlet additionally has the advantagethat the temperature detected thereat makes a statement of greatestvalidity with respect to the characteristics of the liquid delivered bythe pump; moreover, there is no risk of erroneous detection due to heatbuild-up at the liquid outlet as a consequence of the liquid flow takingplace thereat when conveying takes place.

Further, an electronic circuit board can be integrated in the housing,which circuit board carries at least the electronic components necessaryfor electronic commutation of the electric motor as well as optionallythe sensor elements and with which contact by the electrical parts ofthe liquid pump is made by way of press-fit connections. By comparisonwith welded or soldered connections, which are equally conceivable,press-fit connections can be produced at lower cost.

In a preferred and similarly particularly compact embodiment of theliquid pump the liquid outlet of the housing can in addition be orientedtransversely to the axis of rotation of the rotor. Such a radial feedfor the liquid to be conveyed functions without problem and withoutinducting air even in the case of a very low liquid level.

Moreover, it can be provided that the rotor has a permanently magneticouter cylinder selection, which co-operates with the motor winding, aswell as, on the side remote from the housing offset of the statorhousing section, a base section which is formed as an impeller and whichis injection-molded from a magnetic material, which is incorporated inplastic, directly onto a rotor shaft rotatably mounted in the housing.On the one hand, such a rotor can be produced particularly economically.On the other hand, such a shaft solution has advantages—by comparisonwith an axle solution which is equally conceivable in principle and inwhich the rotor rotates on an axis fixed relative to a housing—of such akind that a bearing shank or the like at the rotor for provision of asufficient supporting length is redundant, which in turn is conducive toa short constructional length, and the rotational mounting of the rotorshaft in the housing leads to bearing points which are further apart,this being beneficial for good rotation of the rotor.

In principle, the bearing points can in that case ultimately be formedby bearing bushes or the like in the interior of the housing. However,with respect to low costs it is preferred if the rotor shaft is mountedon either side of the base section at least radially directly in thehousing, in particular on the one hand in the housing offset of thestator housing section and on the other hand in a bearing extension ofthe pump housing section.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail in the following by way ofpreferred embodiments with reference to the accompanying—in partschematic—drawings, in which for simplification of the illustrationelastomeric or elastic parts are illustrated in undeformed state and inwhich:

FIG. 1 shows a perspective view of an electric motor driven liquid pumpaccording to a preferred first embodiment of the invention, innon-mounted state, obliquely from above and the left front with a viewonto a flange surface, which is external to the pump, for fastening to aliquid container such as, for example, a transmission housing;

FIG. 2 shows a plan view of the liquid pump according to FIG. 1, fromabove in FIG. 1;

FIG. 3 shows a sectional view, which is to enlarged scale by comparisonwith the scale of FIG. 2, of the liquid pump according to FIG. 1 incorrespondence with the doubly-stepped section line III-III in FIG. 2 ina state of mounting on a transmission housing, which is illustrated inbroken-away form;

FIG. 4 shows a part sectional view, to a further enlarged scale, of theliquid pump according to FIG. 1 in correspondence with the detail circleIV in FIG. 3, for better illustration of an encircling sealing elementwith a triple function;

FIG. 5 shows a sectional view, which is to enlarged scale by comparisonwith the scale of FIG. 2, of the liquid pump according to FIG. 1 incorrespondence with the section line V-V in FIG. 2;

FIG. 6 shows a sectional view, which is to enlarged scale by comparisonwith the scale of FIG. 3, of the liquid pump according to FIG. 1 incorrespondence with the doubly-stepped section line VI-VI in FIG. 3, butby contrast to FIG. 3 in non-mounted state, i.e. without transmissionhousing and fastening means; and

FIG. 7 shows a longitudinal sectional view of an electric motor drivenliquid pump according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the figures the reference numeral 10 designates in general anelectric motor driven liquid pump for forced lubrication of a manualtransmission for motor vehicles, of which in FIG. 3 merely a lower part,namely a transmission housing 12 (also) serving as a liquid container,is illustrated in broken-away form. The liquid pump 10 is mounted fromthe outside on the transmission housing 12, more preciselyflange-mounted by way of a flange surface 14, which is external to thepump, of a housing 16 of the liquid pump 10, so that a liquid inlet 18and a liquid outlet 20 of the liquid pump 10 protrude into thetransmission housing 12 through an opening 22 in the transmissionhousing 12. Whereas the liquid inlet 18 is disposed below a transmissionoil fill level, which is indicated in FIG. 3 by a horizontal line at 24,in the transmission housing 12, the liquid outlet 20 extends out at thetop above the transmission oil fill level 24, where it is in fluidconnection—in a way which is not shown here—with the distributor system(not illustrated) for the transmission oil.

An electronically commutated electric motor 26 is received in thehousing 16 (see FIGS. 3 and 5) and comprises a substantially cup-shaped,magnetic motor 28, which is rotatable about an axis A of rotation and isprovided at the end with a plurality of curved blade projections 30(cf., in particular, FIG. 6) as means for conveying liquid, a stator 34having a motor winding 32, and a magnetic field sensor 36—which isrequired in a manner known per se for the electronic commutation—forrecognition of the rotational angle position of the rotor 28 (see FIG.3). In that regard, the housing 16 is of multi-part, more preciselythree-part, construction with an upper pump housing section 38, whichhas the liquid inlet 18 and the liquid outlet 20, a middle statorhousing section 40, which carries the annular stator 34 so that this atleast partly surrounds the rotor 28 in coaxial arrangement with respectto the axis A of rotation as seen along the axis A of rotation andbounds together with the pump housing section 38 a liquid chamber 42 inwhich the rotor 28 is arranged by its blade projections 30, and a lowermotor housing section 44, which together with the stator housing section40 bounds an electronics chamber 46 in which, inter alia, the stator 34is located.

In a particularly compact embodiment the stator housing section 40extends, as seen along the axis A of rotation, into the rotor 28 by ahousing offset 48, which is constructed for reception of the magneticfield sensor 36. In addition, as will be similarly described in moredetail in the following, a sealing element 50 is provided at the housing16, which sealing element in a triple function simultaneously seals atthe flange surface 14, which is external to the pump, of the housing 16relative to the transmission housing 12, separates the liquid chamber 42from the electronics chamber 46 and seals the electronics chamber 46with respect to the environment.

Further details with respect to the pump housing section 38, which isconstructed as a plastic material part from a laser-transparent,glass-fiber-reinforced polyphthalamide (PPA 35 GF), can be inferredfrom, in particular FIGS. 3, 5 and 6. Accordingly, the pump housingsection 38 has, radially outwardly, a pump housing flange 52 at whichthe flange surface 14 external to the pump and the flange surface 54internal to the pump are formed on opposite sides. The sealing element50 made from an elastomeric material is secured to the pump housingflange 52 of the pump housing section 38 in a manner still to bedescribed.

The pump housing section 38 is formed with a dome-like elevationradially within the pump housing flange 52 and bounds, in part togetherwith the rotor 28 and the stator housing section 40, in the region ofthe liquid chamber 42 a pump channel 56 which can be substantiallydivided into four regions, namely—as seen in direction from radiallyinwardly to radially outwardly—first, a central, i.e. centered withrespect to the axis A of rotation, substantially funnel-shaped inletregion 58 (see, in particular, FIG. 5), second, a central substantiallyannular acceleration region 60 in which the blade projections 30 of therotor 28 move in operation of the liquid pump 10, and third, asubstantially screw-shaped conveying region 62 (see, for this purpose,also FIGS. 1 and 2), which finally opens into fourth, a tubular outletregion 64 which extends adjacent to the pump housing flange 52substantially parallel to the axis A of rotation. The substantiallyfunnel-shaped inlet region 58, which axially protrudes relative to thecentral acceleration region 60 of the pump channel 56, forms the liquidinlet 18 of the housing 16 at the outer circumferential side, whichinlet is thus oriented substantially transversely to the axis A ofrotation at the rotor 28 and by way of which—as can be best seen inFIGS. 1 and 2—the liquid (here the transmission oil) can run into theliquid pump 10 over almost the full circumference (approximately 360°),i.e. interrupted only by three webs 66 extending in radial direction. Inthe funnel-shaped inlet region 58 the liquid then undergoes a flowdeflection through 90° (from radially in the direction of the axis A ofrotation to axially along the axis A of rotation) until it impinges onthe rotor 28 with its blade projections 30, where a further flowdeflection through approximately 90° takes place (from axially along theaxis A of rotation to radially away from the axis A of rotation). In thecentral acceleration region 60 of the pump channel 56, which as seen insection (FIGS. 3, 5) is bounded on opposite sides in axial direction bythe pump housing section 38 and the rotor 28 to have an approximatelyconstant flow cross-section, the liquid is then as a consequence of theshape of the blade projections 30 accelerated radially outwardly and incircumferential direction in correspondence with the rotationaldirection R of the rotor 28 (see FIG. 6), after which it passes into thesubstantially screw-shaped conveying region 62. In the conveying region62 of the pump channel 56, which is bounded on one axial side by (at thestart) the rotor 28 and the stator housing section 40 and on the otheraxial side as well as at the circumference by the pump housing section38 to have a flow cross-section increasing in correspondence with thecourse of the screw as seen in rotational direction R, the liquid isthen conveyed substantially in circumferential direction to the tubularoutlet region 64. At the start of the outlet region 64 a flow deflectionof the liquid through approximately 90° (from substantially incircumferential direction to axially parallel to the axis A of rotation)then takes place once again, after which the liquid flows along theconstant circular flow cross-section of the outlet region 64 in order tofinally be delivered by the liquid pump 10 by way of the liquid outlet20 formed by the outlet region 64.

According to FIGS. 3 and 5 the pump housing section 38 additionally hasat a central zone, i.e. adjoining the inlet region 58, a bearingprojection 68 for mounting—which is still to be described—the rotor 28.So far as the connection of the injection-molded pump housing section 38with the other parts of the housing 16 is concerned, it must finally bementioned with respect to the pump housing section 38 that the pumphousing flange 52 is provided radially outwardly of the flange surface54 internal to the pump and adjoining this with an encircling groove 70for receiving an encircling collar 72, which is formed to besubstantially complementary as seen in plan view, at the motor housingsection 44. Moreover, the pump housing section 38 has, according toFIGS. 1, 2 and 6, mounts (in FIG. 6 with a dowel centrally at the bottomand a slot at the top right) at 74 for positioning pins 76 (again seeFIG. 6) formed at the stator housing section 40, which pins serve thepurpose of aligning the stator housing section 40 with respect to thepump housing section 38.

The motor housing section 44, which is similarly injection-molded as aplastic material part from a glass-fiber reinforced polyphthalamide (g.PPA 50 GF), is laser-welded to the pump housing section 38—suitablyaligned indirectly by way of the stator housing section 40—and inparticular with its collar 72 encircling in the groove 70 of the pumphousing flange 52 (indicated in FIG. 4 by the cross-hatching at the baseof the groove 70). In that case, according to FIGS. 4 and 5 the pumphousing section 38 is supported by way of the flange surface 54, whichis internal to the pump, of the pump housing flange 52 on an encirclingshoulder 78, which adjoins the collar 72 radially inwardly, of the motorhousing section 44.

In the illustrated embodiment the motor housing section 44 has, radiallyoutwardly, four fastening eyes 80 which are each lined by a metallicsleeve 82 encapsulated in interlocking manner by injection-molding. Asillustrated in FIG. 3, the sleeves 82 in the mounted state of the liquidpump 10 are penetrated by cap screws 84, which are screwed intorespectively associated threaded bores 86—which are distributed aroundthe opening 22—in the transmission housing 12 in order to attach theliquid pump 10 from the outside to the transmission housing 12 and inthat case to also firmly connect the individual parts of the housing 16together. On the other hand, the weld connection between pump housingsection 38 and motor housing section 44 as discussed above servesprimarily as securing during transport.

The motor housing section 44 is provided between the fastening eyes 80on the left in FIGS. 1, 2 and 6 with a plug collar 88 for an electricterminal of the liquid pump 10. In this respect, there can be seen inthe section according to FIG. 5 by way of example that electricalconductors 90 are let into or injection-molded in the motor housingsection 44, which conductors extend from the region of the plug collar88 into the electronics chamber 46. The sectional views according toFIGS. 4 and 5 also show that an electronic circuit board 92 withelectronic components, which are known per se and necessary for the pumpcontrol, is integrated in the electronics chamber 46 of the housing 16.The electronic circuit board 92 itself is contacted relative to theelectrical conductors 90 in the motor housing section 44 by way ofpress-fit connections, of which in FIG. 5 one connection is shown at 94,and is supported on projections 96, which are internally formed at themotor housing section 44 and to which the electronic circuit board 92 isadditionally attached, in part by screws 98. Analogously to thepositioning pins 76 for the pump housing section 38, the stator housingsection 40 also has positioning pins (not able to be seen here), whichare at the bottom in FIGS. 3 and 5 and which engage in associated holes(dowel hole and slot; not shown in the figures) in the motor housingsection 44 and in that case extend through corresponding holes (notillustrated) in the electronic circuit board 92. The electrical parts ofthe liquid pump 10 are similarly contacted by way of press-fitconnections 94 relative to the electronic circuit board 92; of those,there is shown in FIG. 3 by way of example merely the press-fitconnection 94 for a further electrical conductor 90, which is let intoor injection-molded in the stator housing section 40 and with which atemperature sensor 100 is connected. Corresponding electricalconnections (not illustrated in more detail) are present for the motorwinding 32 and for the magnetic field sensor 36.

The stator housing section 40 is also injection-molded as a plasticmaterial part from a glass-fiber-reinforced polyphthalamide (e.g. PPA 50GF). In that regard, not only the said electrical conductors 90, butalso the pole sheets 102 of the stator 34 are embedded byinjection-molding encapsulation by the plastic material of the statorhousing section 40. Only after the injection-molding process is themotor winding 32 mounted, which is economically constructed as anorthogonal layer winding. The stator 34 is completed by a slotted (notshown) metallic ground ring 104, which is drawn with friction fit ontoradially outwardly protruding edges of the pole sheets 102 and inaddition connected by crimping with the edges of the pole sheets 102(not visible in the figures).

The region, which carries the stator 34, of the stator housing section40 surrounds the central housing offset 48 of the stator housing section40 in coaxial positional relationship with respect to the axis A ofrotation while leaving an annular space 106 into which the rotor 28enters. According to FIG. 3, the housing offset 48 is provided at aradially outwardly disposed position thereof, i.e. at a radial spacingfrom the axis A of rotation, with a recess 108, which is open towardsthe motor housing section 44, for reception of the magnetic field sensor36, which can be, for example, a Hall element. According to FIGS. 3 and5, a further bearing projection 110 for journaling the rotor 28 isprovided at the housing offset 48, which is substantially cup-shaped inthe illustrated embodiment, of the stator housing section 40 on the sideremote from the pump housing section 38. The recess 108 for receivingthe magnetic field sensor 36 and the bearing position formed by thebearing projection 110 thus lie within the rotor 28 at a spacing, butadjacent to one another, in a plane extending transversely to the axis Aof rotation. This radial adjacent arrangement of the said functionalelements is also beneficial for the flat, i.e. nested constructionalform of the liquid pump 10. Beyond that, the magnetic field sensor 36 isarranged near the outer wall of the rotor 28, which by virtue of thespacing of maximum size from the axis A of rotation on the one hand andthe proximity to the rotor 28 on the other hand is conducive to a goodquality of the detected signal.

According to FIGS. 2, 3 and 6, in addition a sub-region 112 of thestator housing section 40 protrudes, as seen in radial direction,adjacent to the stator 34 and axially in direction of the pump housingsection 38 in ramp-like manner beyond the rest of the stator housingsection 40 and thus forms a gradual transition, which reduces powerlosses, between the screw-shaped conveying region 62 and the tubularoutlet region 64 of the pump channel 56. According to FIGS. 3 and 6 thissub-region 112 of the stator housing section 40 is provided with areceiving recess 114, which is open towards the motor housing section44, for the temperature sensor 100 so that the latter is integrated inthe housing 16 of the liquid pump 10 near the liquid outlet 20.

Finally, the stator housing section 40 has, radially outwardly, a statorhousing flange 116 which is clamped in place in sandwich-like mannerbetween the pump housing section 38 and the motor housing section 44 andwhich radially centers the stator housing section 40 in an associatedstep 118 at the motor housing section 44 with respect to the axis A ofrotation.

Further details with respect to the encircling sealing element 50, whichfor simplification of the illustration is shown undeformed, areillustrated in FIGS. 4 and 6. According to those, the pump housingflange 52 of the pump housing section 38 starting from the flangesurface 14, which is external to the pump, of the housing 16 is providedwith an encircling depression or groove 120 for reception of a firstsealing section 122 of the sealing element 50, which protrudes by twosealing lips 124, 126, i.e. a radially inner sealing lip 124 and aradially outer sealing lip 126, beyond the flange surface 14 external tothe pump so as to provide sealing relative to the transmission housing12. Moreover, the pump housing flange 52 starting from the flangesurface 54 internal to the pump is provided with a further encirclingdepression or groove 128 for receiving a second sealing section 130 ofthe sealing element 50. The latter protrudes by two sealing lips 132,134 beyond the flange surface 54 internal to the pump, of which one,radially inner sealing lip 132 co-operates with the stator housingflange 116 of the stator housing section 40 so as to separate the liquidchamber 42 from the electronics chamber 46. The other, radially outersealing lip 134, thereagainst, co-operates with an associated shoulder136 of the motor housing section 44 so as to seal off the electronicschamber 46 from the environment. In that case, the second sealingsection 130 of the sealing element 50 extends over or covers the centralregion between the stator housing flange 116 of the stator housingsection 40 and the step 118 at the motor housing section 44 in radialdirection with respect to the axis A of rotation of the rotor 28, inwhich case as a consequence of deformation of the sealing lips 132, 134a defined biasing force is also produced between the individual parts ofthe housing 16.

In the illustrated embodiment the sealing element 50 is injection-moldedat the pump housing flange 52 of the pump housing section 38 to beinterlocking. For that purpose, formed in the pump housing flange 52between the encircling groove 120 at the flange surface 14 external tothe pump and the encircling groove 128 at the flange surface 54 internalto the pump is a plurality of openings 138, which are preferablyuniformly spaced apart in the circumferential direction, i.e. as seenalong the grooves 120, 128, and which connect the grooves and arepenetrated by the elastomeric material of the sealing element 50 byinjection molding so as to interconnect the first sealing section 122and the second sealing section 130 of the sealing element 50 by way of amaterial bond.

Finally, further details with respect to the rotor 28 and the mountingthereof in the housing 16 are shown by, in particular, FIG. 5. The rotor28 has a permanently magnetic outer cylinder section 140, whichco-operates in a manner known per se with the motor winding 32 of thestator 34, as well as a base section 142 constructed as an impeller withthe blade projections 30 on the side remote from the housing offset 48of the stator housing section 40, and is made from a magnetic materialwhich is incorporated in plastic material and which is directlyinjection-molded on a metallic (preferably steel) rotor shaft 144, whichis rotatably mounted in the housing 16, with conjunctive formation ofthe blade projections 30. The rotor shaft 144 is journaled radiallydirectly, i.e. without bearing bushes or the like, in the housing 16 oneither side of the base section 142, namely on the one hand in acylindrical recess 146 at the bearing projection 110 in the housingoffset 48 of the stator housing section 40 and on the other hand in acylindrical recess 148 at the bearing projection 68 of the pump housingsection 38. In that regard, the rotor shaft 144 is supported in FIG. 5axially at the bottom, i.e. at the end, on the base of the recess 146 inthe bearing projection 110. In FIG. 5 at the top a thrust washersurrounding the rotor shaft 144 can be provided between the base section142 of the rotor 28 and the bearing projection 68, by way of whichwasher the rotor 28 is axially supported, in operation of the liquidpump 10, at the bearing projection 68 when the rotor 28 is raisedagainst gravitational force due to the pressure conditions arisingthereat.

In the following, the liquid pump 10 according to the second embodimentshall be described with reference to FIG. 7 only to the extent that itdiffers significantly from the first embodiment described in detailabove with reference to FIGS. 1 to 6. In that regard, the same referencenumerals designate components or subassemblies of the second embodimentthe same as or corresponding with those of the first embodiment.

The significant differences here concern the construction of the statorhousing section 40 in the region of the rotor 28 and the mounting—whichis at the bottom in FIG. 7—of the rotor 28 at the stator housing section40. In the second embodiment the housing offset 48 is not formed to besubstantially cup-shaped, but has two sections, which are formedintegrally at the stator housing section 40 by way of a base 151, thebase being circular in plan view as seen in the direction of the axis Aof rotation, and by which the housing offset 48—again as seen along theaxis A of rotation—extends into the rotor 28, namely a central bearingsection 152 and a sensor section 154, which is radially spaced from thebearing section 152 with respect to the axis A of rotation, in thevicinity of the cylinder section 140 of the rotor 28.

The bearing section 152 is open towards the rotor 28 and provided at theaxial height of the sensor section 154 with the cylindrical recess 146for direct radial mounting of the rotor shaft 144. However, here therotor shaft 144 does not extend as far as the bottom or base of thecylindrical recess 146 in the bearing section 152, but ends beforehandat an axial spacing therefrom. For that purpose the bearing section 152is constructed to be longer than the bearing projection 110 in the firstembodiment and ends, as seen in the direction of the axis A of rotation,only shortly in front of the base section 142 of the rotor 28. A secondthrust washer 158, which surrounds the rotor shaft 144 and by way ofwhich the rotor 28 can be axially supported on the bearing section 152,is inserted between an annular end surface 156 of the bearing section152 and the base section 142 of the rotor 28.

On the other hand, the sensor section 154 is provided with the recess108, which is open towards the electronics chamber 46 or the electroniccircuit board 92, for receiving the magnetic field sensor 36 and extendsto only half the height of the cylinder section 140 of the rotor 28. Asa result, also in this embodiment the magnetic field sensor 36 and theradial bearing point for the rotor shaft 144 are arranged in verycompact constructional form in the rotor 28 on the side of the statorhousing section 40 in one plane which extends transversely orperpendicularly to the axis A of rotation.

An electric motor driven liquid pump usable for forced lubrication of amanual transmission for motor vehicles includes a housing, which has aliquid inlet and a liquid outlet, and an electronically commutatedelectric motor received therein. The latter has a substantiallycup-shaped magnetic rotor, which is rotatable about an axis of rotation,with a pump for conveying liquid, an annular stator, which has a motorwinding and which as seen along the axis rotation at least partlysurrounds the rotor in coaxial arrangement with respect to the axis ofrotation, and a magnetic field sensor for positional recognition of therotor. The housing has in that connection a stator housing section whichcarries the stator, separates this from the liquid chamber in which therotor is arranged, and as seen along the axis of rotation extends intothe rotor by a housing offset which is constructed for reception of themagnetic field sensor so that the liquid pump overall has only a lowconstructional height.

Variations and modifications are possible without departing from thescope and spirit of the present invention as defined by the appendedclaims.

We claim:
 1. An electric motor driven liquid pump comprising a housing,which has a liquid inlet and a liquid outlet, and an electronicallycommutated electric motor, which is received therein and which comprisesa magnetic rotor shaped for conveying liquid upon rotation, the rotorbeing rotatable about an axis of rotation, an annular stator having amotor winding and at least partly enclosing the rotor in coaxialarrangement with respect to the axis of rotation as seen along the axisof rotation, and a magnetic field sensor for recognition of therotational position of the rotor, wherein the housing has a statorhousing section which carries the stator, separates the stator from aliquid chamber in which the rotor is arranged, and as seen along theaxis of rotation extends into the rotor by a housing offset formed toreceive the magnetic field sensor, and the magnetic field sensortherein, said offset having a cavity separated by said stator housingfrom said liquid chamber with said magnetic field sensor therein alsoseparated from said liquid chamber by said stator housing, said statorhousing section, said stator, and said rotor each having a respectiveaxial extent is arranged within the respective axial extents of each ofthe stator housing section, the stator, and the rotor for sensing therotational position of the rotor with respect to the stator.
 2. Anelectric motor driven liquid pump according to claim 1, wherein thehousing is constructed to be flange-mounted on a liquid container by wayof a flange surface external to the pump and comprises in multi-partconstruction in addition to the stator housing section a pump housingsection, which has the liquid inlet and the liquid outlet and whichtogether with the stator housing section bounds the liquid chamber, anda motor housing section, which together with the stator housing sectionbounds an electronics chamber in which at least the stator is located.3. An electric motor driven liquid pump according to claim 2, whereinthe pump housing section and the motor housing section are constructedas plastic material parts and are welded together.
 4. An electric motordriven liquid pump according to claim 2, wherein the stator housingsection has a stator housing flange which is clamped in place betweenthe pump housing section and the motor housing section and centers thestator housing section at the motor housing section with respect to theaxis of rotation.
 5. An electric motor driven liquid pump according toclaim 2, wherein a sealing element is provided, which sealing elementsimultaneously seals the flange surface, which is external to the pump,of the housing relative to the liquid container, separates the liquidchamber from the electronics chamber and seals the electronics chamberrelative to the environment.
 6. An electric motor driven liquid pumpaccording to claim 5, wherein the flange surface, which is external tothe pump, of the housing is provided with an encircling groove forreception of a first sealing section of the sealing element, whichprotrudes by two sealing lips beyond the flange surface external to thepump so as to seal relative to the liquid container.
 7. An electricmotor driven liquid pump according to claim 5, wherein the sealingelement which is made from an elastomeric material is attached to thepump housing section, by being injection molded at the pump housingsection to interlock therewith.
 8. An electric motor driven liquid pumpaccording to claim 1, wherein pole sheets of the stator are embedded inthe stator housing section, which is made from plastic material, byinjection-molding encapsulation with plastic material.
 9. An electricmotor driven liquid pump according to claim 1, wherein a temperaturesensor is integrated in the housing in proximity to the liquid outletand received in a receiving recess in the stator housing section.
 10. Anelectric motor driven liquid pump according to claim 1, wherein anelectronic circuit board with which the electrical parts of the liquidpump are contacted by way of press-fit connections is integrated in thehousing.
 11. An electric motor driven liquid pump according to claim 1,wherein the liquid inlet of the housing is oriented transversely to theaxis of rotation of the rotor.
 12. An electric motor driven liquid pumpaccording to claim 1, wherein the rotor has a permanently magnetic outercylinder section co-operating with the motor winding and a base section,which is constructed as an impeller on the side remote from the housingoffset of the stator housing section and is injection-molded from amagnetic material, which is incorporated in plastic material, directlyon a rotor shaft rotatably mounted in the housing.
 13. An electric motordriven liquid pump, comprising a housing, which has a liquid inlet and aliquid outlet, and an electronically commutated electric motor, which isreceived therein and which comprises a magnetic rotor shaped forconveying liquid upon rotation, the rotor being rotatable about an axisof rotation, an annular stator having a motor winding and at leastpartly enclosing the rotor in coaxial arrangement with respect to theaxis of rotation as seen along the axis of rotation, and a magneticfield sensor for recognition of the position of the rotor, wherein thehousing has a stator housing section which carries the stator, separatesthe stator from a liquid chamber in which the rotor is arranged, and asseen along the axis of rotation extends into the rotor by a housingoffset formed to receive the magnetic field sensor, and the magneticfield sensor is arranged within the axial confines of both the statorhousing section of the housing and the stator, wherein a sealing elementis provided, which sealing element simultaneously seals the flangesurface, which is external to the pump, of the housing relative to theliquid container, separates the liquid chamber from the electronicschamber and seals the electronics chamber relative to the environment,wherein the pump housing section has a pump housing flange at which theflange surface external to the pump and a flange surface internal to thepump are formed on opposite sides, the flange surface internal to thepump being provided with an encircling groove for reception of a secondsealing section of the sealing element, which protrudes by two sealinglips beyond the flange surface internal to the pump, one sealing lipco-operating with the stator housing section so as to separate theliquid chamber from the electronics chamber and the other sealing lipco-operating with the motor housing section so as to seal theelectronics chamber relative to the environment.
 14. An electric motordriven liquid pump, comprising a housing, which has a liquid inlet and aliquid outlet, and an electronically commutated electric motor, which isreceived therein and which comprises a magnetic rotor shaped forconveying liquid upon rotation, the rotor being rotatable about an axisof rotation, an annular stator having a motor winding and at leastpartly enclosing the rotor in coaxial arrangement with respect to theaxis of rotation as seen along the axis of rotation, and a magneticfield sensor for recognition of the position of the rotor, wherein thehousing has a stator housing section which carries the stator, separatesthe stator from a liquid chamber in which the rotor is arranged, and asseen along the axis of rotation extends into the rotor by a housingoffset formed to receive the magnetic field sensor; wherein the housingis constructed to be flange-mounted on a liquid container by way of aflange surface external to the pump and comprises in multi-partconstruction in addition to the stator housing section a pump housingsection, which has the liquid inlet and the liquid outlet and whichtogether with the stator housing section bounds the liquid chamber, anda motor housing section, which together with the stator housing sectionbounds an electronics chamber in which at least the stator is located;wherein a sealing element is provided, which sealing elementsimultaneously seals the flange surface, which is external to the pump,of the housing relative to the liquid container, separates the liquidchamber from the electronics chamber and seals the electronics chamberrelative to the environment; wherein the flange surface, which isexternal to the pump, of the housing is provided with an encirclinggroove for reception of a first sealing section of the sealing element,which protrudes by two sealing lips beyond the flange surface externalto the pump so as to seal relative to the liquid container; and whereina plurality of openings spaced apart in circumferential direction isprovided between the encircling groove at the flange surface external tothe pump and the encircling groove at the flange surface internal to thepump, the elastomeric material of the sealing element beinginjection-molded through the openings so as to interconnect the firstsealing section and the second sealing section of the sealing element.15. An electric motor driven liquid pump according to claim 14, whereinpole sheets of the stator are embedded in the stator housing section,which is made from plastic material, by injection-molding encapsulationwith plastic material.
 16. An electric motor driven liquid pumpaccording to claim 15, wherein a temperature sensor is integrated in thehousing in proximity to the liquid outlet and received in a receivingrecess in the stator housing section.
 17. An electric motor drivenliquid pump according to claim 16, wherein an electronic circuit boardwith which the electrical parts of the liquid pump are contacted by wayof press-fit connections is integrated in the housing.
 18. An electricmotor driven liquid pump according to claim 17, wherein the liquid inletof the housing is oriented transversely to the axis of rotation of therotor.
 19. An electric motor driven liquid pump according to claim 18,wherein the rotor has a permanently magnetic outer cylinder sectionco-operating with the motor winding and a base section, which isconstructed as an impeller on the side remote from the housing offset ofthe stator housing section and is injection-molded from a magneticmaterial, which is incorporated in plastic material, directly on a rotorshaft rotatably mounted in the housing.
 20. An electric motor drivenliquid pump according to claim 19, wherein the rotor shaft is mounted onboth sides of the base section at least radially directly in thehousing, namely, in the housing offset of the stator housing section andin a bearing projection of the pump housing section.
 21. An electricmotor driven liquid pump according to claim 14, wherein the housingoffset is provided with a recess having an open end for reception of themagnetic field sensor.
 22. An electric motor driven liquid pumpaccording to claim 21, wherein the recess has the open end facingtowards the motor housing section; and said recess is positioned at aradially outward position within said housing offset.
 23. An electricmotor driven liquid pump comprising a housing, which has a liquid inletand a liquid outlet, and an electronically commutated electric motor,which is received therein and which comprises a magnetic rotor shapedfor conveying liquid upon rotation, the rotor being rotatable about anaxis of rotation, an annular stator having a motor winding and at leastpartly enclosing the rotor in coaxial arrangement with respect to theaxis of rotation as seen along the axis of rotation, and a magneticfield sensor for recognition of the rotational position of the rotor,wherein the housing has a stator housing section which carries thestator, separates the stator from a liquid chamber in which the rotor isarranged, and as seen along the axis of rotation extends into the rotorby a housing offset formed to receive the magnetic field sensor therein,said offset having a cavity separated by said stator housing from saidliquid chamber with said magnetic field sensor therein also separatedfrom said liquid chamber by said stator housing, said stator housingsection and said stator each having a respective axial extent, and themagnetic field sensor is arranged within the respective axial extents ofboth the stator housing section of the housing and the stator forsensing the rotational position of the rotor with respect to the statorwherein the housing offset is provided with a recess having an open endfor reception of the magnetic field sensor.
 24. An electric motor drivenliquid pump according to claim 23, wherein the recess has the open endfacing towards the motor housing section; and said recess is positionedat a radially outward position within said housing offset.
 25. Anelectric motor driven liquid pump comprising a housing, which has aliquid inlet and a liquid outlet, and an electronically commutatedelectric motor, which is received therein and which comprises a magneticrotor shaped for conveying liquid upon rotation, the rotor beingrotatable about an axis of rotation, an annular stator having a motorwinding and at least partly enclosing the rotor in coaxial arrangementwith respect to the axis of rotation as seen along the axis of rotation,and a magnetic field sensor for recognition of the rotational positionof the rotor, wherein the housing has a stator housing section whichcarries the stator, separates the stator from a liquid chamber in whichthe rotor is arranged, and as seen along the axis of rotation extendsinto the rotor by a housing offset formed to receive the magnetic fieldsensor, and wherein the housing offset is provided with a recess havingan open end for reception of the magnetic field sensor and a bearingprojection for journaling the rotor, and wherein said recess and abearing position formed by said bearing projection lie within the rotorat a spacing, but adjacent to one another, in a plane extendingtransversely to the axis of rotation.
 26. An electric motor drivenliquid pump according to claim 25, wherein the recess has the open endfacing towards the motor housing section; and said recess is positionedat a radially outward position within said housing offset.